Angular

Custom Decorators in Angular: Enhance Code Reusability and Maintainability

Introduction

In Angular, @Component, @Injectable etc are built in decorator. However, you can also write your custom decorator. Such functions let you wrap up repetitive logic in reusable functions and thus help to improve code reusability and their maintainability.

What are Custom Decorators?

In other words a custom decorator is a function we can invoke on top of a class, property or method to provide metadata or change their originating behaviour. After that you follow the same syntax as Angular’s built in decorators but you define your own logic.

Why Use Custom Decorators?

Reusability: Encapsulate repetitive logic in one place.

It makes sure that the code is free of boilerplate code and keep components clean.

Force the same behaviour throughout several components or services.

How to Create a Custom Decorator?

The simple logging decorator we want to build will also log the method call as well as the arguments passed to them.

Create the Decorator

export function LogMethod() {
return function (target: any, propertyKey: string, descriptor: PropertyDescriptor) {
const originalMethod = descriptor.value;
descriptor.value = function (...args: any[]) {
console.log(`Calling ${propertyKey} with arguments:`, args);
const result = originalMethod.apply(this, args);
console.log(`Result of ${propertyKey}:`, result);
return result;
};
return descriptor;
};
}

Use the Decorator in a Component or Service

import { Component } from '@angular/core';
import { LogMethod } from './log-method.decorator';
@Component({
selector: 'app-demo',
template: `<button (click)="calculate(5, 3)">Calculate</button>`
})
export class DemoComponent {
@LogMethod()
calculate(a: number, b: number): number {
return a + b;
}
}
When you click the button, you’ll see logs like:
Calling calculate with arguments: [5, 3]
Result of calculate: 8

Conclusion

Angular custom decorator is a way to add our own logical to class, method, properties. A good written code is only a code that is tidy, consistent and maintainable.

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